Contrasting Observation in Culturable Aerobic and Micro-Aerophilic Heterotrophic Fish Gut-Bacteria:Intestine-Breathing Lepidocephalichthys guntea (Hamilton Buchannan) Versus Gill-Breathing Labeo rohita

Lepidocephalichthys guntea exhibits exceptional adaptive characters and can survive in flowing or stagnant waters as well as muddy hypercarbic condition resembling a desiccating habitat. This study was conducted to relate aerophilic (both aerobic and microaerophilic) bacterial density in the gut of L. guntea with dissolved oxygen (DO₂) content. Aerophilic bacterial density in the gut of L. guntea was found independent of DO₂ content, as the air pocket(s) present in the gut balances the deficit of oxygen obtained through gill respiration. This phenomenon was found to be reversed in gill-breathing fish like Labeo rohita because the additional mechanism to breathe air via gut is absent. The density of both the categories of culturable aerophilic bacteria was found to be significantly reduced in the gut of L. rohita gut in low DO₂ condition of its habitat.